Breaker mechanism



Jan. 15', 1946. Y 2,393,049

BREAKER MECHANISM Filed Feb. 15, 1942 2 Sheets-Sheet ,1

y I 126 gm Y 9 130" l T T 10 AA/$10 Mi/w NiM v I 6 7 8 9 6a 74 $84 17 d I 76 l 55 95 I WITNESSES: INVENTOR John W May.

ATTORN Jan. 15, 1946, J. w. MAY

BREAKER MECHANISM Filed Feb. 13, 1942 2 Sheets-Sheet 2 INVENTOR J0/m W/Way.

WITNESSES:

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ATTORNEY Patented Jan. 15, 1946 UNI TED STATES PATENT OFFICE 2,393,049 BREAKER MECHANISM John W. May, Durham, N.1C., assignor to Westing'house Electric Corporation, East Pittsburgh, Pa.-, a corporation of Pennsylvania Kpplication February is, 1942, Serial No. 430,7 12

7 Claims.

This invention relates to electrical distribution s stem and it has particular relation to an electrical distribution system having a plurality or circuit breakers designed for coordinated operation under predetermined "conditions of the assaciated distribution system.

In certain electrical distribution systems, such, {or example, as those shown in Ludwig and Ma Patent 2,331,209 for an mrect'rical distributing system, 'a. plurality of circuit breakers are desired which trip "in aprede't'er'mined sequence when a predetermined fault occurs on the system. For example, reference may be made to a network distribution system wherein a plurality of transfarmers are 'connectedt'o a common load circuit through transformer circuit breakers. The load circuit is sectionalized between points of connection of adjacent pairs of transformers by means of sectionalizing circuit breakers. When a fault occurs on the load circuit, certain of the s'ectionalizing circuit breakers trip in advance of their associated transformer circuit breakers in order to relieve the associated transformer "circuit breakers of load current. Asystem of this type is disclojse'din the Parson application, Serial No. 342,938, filed June 28, 1940, and assigned to the Westinghouse Electric 8: Manufacturing Com- D lly.

As a further example of a system wherein circuit breakers are sequentiall operated, reference may be ade to the Bergvall-application, Serial No. 406,136, filed August 9, 1941, and assigned to the Westinghouse Electric 8: Manufacturing Company. In the Bergvali distribution system, a pluranty or transformers are connec ed w com 1 embodiment of the invention, the cperating handies of a transformer breaker and a sctionalizing breaker are connected by means of a link and the transformer breaker is provided with a lockascents cooperative with a i''s'ilint connection between its assisting handle and its circuit' breaking contacts. Opening of the sectionalizing breaker results in the application o f anjopening force to the transformer breaker through the above-mentioned link but an electromagnet controls the actual circuit-opening operation of the transformer "breaker until after movement to open position of the sectionalizing breaker. The electrcmagnet may be controlled by meansresfponsive to a predetermined condition of the elec trical distribution system, such as the voltage of the line supplying the transformer. I

The invention iurther contemplates the provision of a 'reclosing mechanism which {o erates to re'close the sectiona'liz ing breaker aft'er a brief interval. Reclosure of this circuit breaker, in turn, conditions the transformer breaker for reclcsure provided the voltage available at the lat.- ter circuit breaker is: above a predetermined value. A It is, therefore, an object of the invention to provide an improved electrical distribution system having a plur'ality 'of circuit breakers designed for coordinated operation, 7 M V It is a furtherobje'ct or the invention to provide a plurality of circuit breakers interconnected by a link operating to condition one of the circuit breakers for an operation in response to an operation of the second of the circuit breakers.

It is a still further object of the invention to provide a plurality of circuit breakers designed for coordinated operation wherein reclosure of one of the circuit breakers conditions a remaining circuit breaker for reclosure, V

It is still another object ofthe invention to provide a pair of circuit breakers designed "for coordinated operation wherein operation of one circuit breaker conditions the remaining circuit breaker for operation, and wherein operation of the second circuit breakerfurtheris controlled in accordance with a predetermined variable Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic View in single line of an electrical distribution system suitable for the application of this invention;

Fig. 2 is a schematic view with parts in elevation showing a pair of interconnected circuit breakers embodying the invention;

Fig. 3 is a detailed view in endelevation of a portion of one of the circuit breakers of Fig 2; and

Fig. 4 is a schematic view in single line illustrating a modification of the electrical distribution system of Fig. 1.

Referring to the drawings, Figure 1 shows a distribution system supplied with electrical energy from a single source i of electrical energy which is connected to a branch feeder circuit or bus 2. Although the invention is applicable to systems employing alternating or direct current and to systems energized b polyphase or single phase energy, it is assumed for the purpose of discussion that Fig. 1 represents a single phase alternating-current system.

As shown in Fig, l, the branch feeder circuit or bus 2 is connected to a distribution circuit 3 through a plurality of transformers 4 to 9, each having a primary winding connected to the branch feeder circuit or bus. If desired, fuses 10 may be provided between each primary winding and the branch feeder circuit or bus 2.

The distribution circuit 3 includes a plurality of load circuits 1 l to 16 which are interconnected by a suitable tie circuit ll. Each of the transformers has its secondary winding connected to the distribution circuit through a separate main or transformer circuit breaker 4a to So. By inspection cf Fig. 1, it will be observed that the transformers 4 to 9 are connected in parallel for the purpose of energizing the distribution circuit 3.

In order to increase the flexibility of the system illustrated in Fig. 1, the tie circuit i! sectionalized by means of sectionalizing circuit breakers positioned between the points of connection of the transformers to the distribution circuit. In the specific embodiment of Fig. 1, each of the transformer circuit breakers 4a to 9a has associated therewith a sectionalizing circuit breaker 4b to 9?).

Each sectionalizing breaker is designed to con trol in part the opening of its associated transformer breaker. For example, the sectionalizing circuit breaker ab controls in part the opening of the transformer circuit breaker 4a. In an analogous manner, the sectionalizing circuit breaker 5b controls in part the opening of the transformer circuit breaker 5a.

With this brief description of the system of Fig. 1 in mind, it is believed that a description of the operation of the system will assist in an understanding of the invention. It will be assumed first that the system of Fig. 1 is in normal operation with all of the circuit breakers closed.

Should a fault F occur on the distribution circuit, as indicated adjacent the load circuit l2, an excessive current flows through the adjacent transformers 4 and 5. Since the sectionalizing circuit breaker 4b is designed to open in advance of the transformer circuit breaker 4a in response to such a fault, the sectionalizing circuit breaker is the first of these two breakers to open. The opening of the sectionalizing circuit breaker 4b relieves the transformer 4 of the excessive burden imposed by the fault F. Consequently, the transformer circuit breaker 4a remains closed, the transformer 4 continues to supply electrical energy to the load circuit ll without interruption.

The excessive current flowing through the transformer 5 tends to trip the associated transformer circuit breaker 5a. However, because of the correlation between the opening of this circuit breaker and that of the associated section- -izing circuit breaker 5b, the sectionalizing circuit breaker 5b is the first to trip. This disconnects the fault F from the portion of the distribution circuit to the right of the sectionalizing circuit breaker 5b as viewed in Fig. l. Consequently, the transformers 6 to 9 continue to supply current to the loads l3 to 16 without interruption.

By inspection of Fig. 1, it will be noted that opening of the sectionalizing circuit breaker 55 does not affect the connection between the fault F and the transformer circuit breaker Ea. Consequently, the circuit breaker 5a trips to disconnect the transformer 5 from the fault F from the associated load circuit 12. This means that the entire distribution circuit 3 with the exception of the load circuit 22 continues to receive electrical energy without interruption. To asthe entire distribution circuit 3 with the excepsure proper functioning of this system, it is desirable that the opening of the various circuit breakers be effected with time delay and preferably with inverse time delay.

To illustrate the desirability of the sectionalizing circuit breakers, let it be assumed that such circuit breakers are not provided. If the loads on the load circuits [3 and I4 are heavy, the resultingburden on the adjacent transformer 6 after the circuit breaker 5a trips may be sufficient to open the transformer circuit breaker 6a. This opening of the transformer circuit breaker in wouldtransferthe excessiveloadto the next transformer 1. The opening of the transformer circuit breaker 1a in response to this excessive burden would in turn transfer an excessive burden to the transformer B. This continued transfer or cascade effect would continue until all of the transformer circuit breakers 6a to So had opened with a resulting termination of service to the load circuits l3 to IS.

The cascade opening of the circuit breakers 6a to So is prevented by operation of the associated sectionalizing circuit breakers. If the loads on the load circuits l3 and I4 are heavy, the sectionalizing circuit breaker 62) opens in advance of the transformer circuit breakers 6a. This relieves M122" ii the circuit 14 and the transformer continues to supply electrical energy to the load circuit l3 without interruption. Consequently, by operation of the sectionalizing circuit breakers, a reasonably satisfactory distribution of load is assured for the system.

Although each sectionalizing circuit breaker may be displaced appreciably from its associated transformer circuit breaker, preferably they are located adjacent each other and conveniently they may be included in the same transformer housing. A suitable construction for these circuit breakers and their control circuits are illustrated in Fig. 2. Since each group comprising a transformer circuit breaker and its sectionalizing circuit breaker is similar to the remaining groups, a description of one of the groups, such as that including the circuit breakers 4a and 4b, will suffice.

Ln the transformer 4 is illustrated as connected to the stationary contacts 20 of the two-pole transformer circuit breaker 4a through conductors 2| and 23. The two-pole construction of this circuit breaker is illustrated more clearly in Fig. 3. These stationary contacts 20 are positioned in the path of a pair of movable contacts 22 which are mounted at one end of an arm 24. The arm 24 is pivoted on a stationary pivot 26 for pivotal movement from the position wherein the contacts 22 and 20 are in engagement, as shown in full lines in Fig. 2, to a position wherein the contacts are spaced as illustrated in dotted lines in Fig. 2. In the latter position, the arm 24 is engagement with a stationary abutment 28.

Movement of the arm 24 between its open and closed positions is controlled by a. pair of arms 30 aoesp ie and-i2 which forma togg le mechanism. The arm II has one end plvotally connected to 2! bymeans of a pin. "rheremainin'gendotthe arm 80 is pivotaily connected to one end ottlz'e arm?! by means of oi-pin 36. Aplvot pln'l i'eonnects the remaining end or the arm 3 2toa lever which is pivoted for movement about a stationary pin -42.

Movement of the lever 40 is from the position illustrated in full lines ln'Fig. "2 toapds'ition'flluk trated'ln dotted wherein the lever engages a fixed abutment 44.

Operation oi. the toggle mechanism formed by the arms 32 and 38 is effected by a tension spring '45 which has-one end connected to the pin 56 and a second end connected to a log 48 carried "by an operatm'g arm to. This o erating arm 50 has one endpivotally connected to a stationary shaft 52 which ermits movement of the arm 51) clockwise from the position shown in full lines In Fig. '2. The extreme counterclockwise osition of the arm 50 is determined by fixed abutment 5!.

Operation of the toggle mechanism formed by the arms and 32 is determined by the position of the lug 48 with respect to the pin 38. It the lug i8 is on the left of the pin 38 as illustrated in full lines in Fig. 2, the line of action of the spring it urges the pin '36 to the left to a position determined by a fixed abutment 58. In this position, the arms 30 and 32 are substantially in vertical alignment and the contacts 20 and 22 are closed.

If the lug 48 is on the right of the pin 38, the line of action of the spring is such that the force applied to the pin 36 breaks the toggle mechanism formed by the arms 30 and 32 and moves the arms to the positions shown in dotted lines which are designated by the reference characters 30d and 32d. Such movement of the lug Ill with respect to the pin 38 is effected by actuation of the operating arm in a clockwise direction about pivot 52.

Should the pivot pin 38 move to the leit of the lug 48, as indicated by dotted lines in Fig. 2, the line of action of the spring it is such that "the toggle mechanism formed by the arms "30 and 32 again isbroken and the arms 30 and 32 move to the positions illustrated in dotted lines and desi nated by the reference characters 3021 and 3217. This movement of the pin 38 is effected by actuatlon of the lever 40 from the position illustrated in full lines in Fig. 2 to the position illustrated in dotted lines. It will be observed that with the arms in the positions designated by the reference characters 30b and 321;, the arm 24 of the circuit breaker again is in the position illustrated in dotted lines and the contacts 2'1! and 22 are separated.

Summarizing the operation of the circuit breaker la, if the arm and the lever 40 are in the positions illustrated in full lines in Fig. 2, the circuit breaker is closed.

Should the operating arm 50 be actuated to the clockwise position above-mentioned, the circuit breaker Ia would be opened.

Furthermore, if the lever 40 moves to the position shown in dotted lines in Fig. 2, the breaker 4a.- would open regardless of the position of the operating arm 50.

Normally, the lever 40 is maintained in the position illustrated in full lines by means of a I lug 0 positioned in the path of movement of 'a tongue 62 carried by the lever 40. The lug is positioned at one end of a bimetallic spring 6 which has its other end fixed to an abutment 66. Consequently, under normal conditions, operation of the circuit breaker lais controlled by-actuation of the operating arm 51!. v

The section-aiming circuit breaker '4?) is similar in "construction to the portion of the circuit breaker -'4a thus 'far specially described. Simiia'r parts of the circuit breaker 4b are designated by similar reference characters which are distinguished by prime marks.

Operation. of the circuit breaker 4a is controlled in part by a link 68 which is pivotally connected to a pin 10 positioned at one end of the arm *50. An operating force in the direction of the arrow 12 exerted on the pin TB through the link 68 urges the arm 50 towards an "open position, and con-- ditions the circuit breaker id for an opening operation. Conv'ersely 'a force operating in the direction of the arrow H on the link 68 urges the operating arm 50 towards the abutment '54, what may be termed a close position, and'c'onditions the circuit breaker to for "a closing oper- 'ation.

Movement of the operating arm 2! under the influence of the openin and closing forces rep; resented by the arrows i2 and H is controlled by a lock T6 pivotally mounted on a stationary shaft '18 for movement from the position illiljse trated in full lines in Fig. 2 to the p'o'sition partly illustrated in dotted lines. This lock is 'paitrof a control electromagnet having an annature portion Bil positioned for attraction by magnetic flux produced by a magnetic structure 82 one 'or more energizing windings '83. The lock 16 has fingers 88 and 95 biased towards the position illustrated by means of a spring 86.

Locking fingers 88 and '9!) carried by the latch 76 are positioned for movement into and out of the path of a pin 92 which is carried bya lever B! mounted on a fixed pivot 96. One endot the lever 9 is pivotally connected through the plh 95 and link 51 to the pivot 36 between links 30 and 32. v

By inspection of Fig. 2, it will be observed that when the armature '80 is attracted by the magnetic structure 82, the locking finger '88 is ositioned in the path of travel of the pin 92 and pre- Vents movement of the operating a m 24 away from its circuit breaker closed position. Similarly, if the circuit breaker is open and the lock 16 is in its dotted-line position, the locking finger 90 is in the path of movement of the pin 92 and retains the operating arm 24 in its circuit breaker open position.

Energizati'on of the winding '8'! be in accordance with any desired variable iiil'antity to prevent an opening o eration or the circuit breaker 4a when the variable quantity is above a predeternnned value. such a variable quantity may be current flowing through the circuit breaker contacts, voltage across the circuit breaker contacts, voltage of the line connected to the circuit breaker 4a, or may include both voltage and current. For the purpose of this discussion. it will be assumed that the winding M is energized in accordance with voltage of the line, and that the magnetic structure 82 is designed to pick up its armature to the full-line. position when the voltage rises above a predetermined value, such as 80% of its normal rated value. As a further example, the magnetic structure 82 may be designed to permit the armature 88 to drop out or move to its dotted-line position when the voltage across the secondary or the associated transformer 4 drops below a predetermined value, such a 25% of its normal rated value. Under such circumstances, the lock 16 permits an opening operation of the associated circuit breaker 4a only when the voltage across the secondary of the transformer 4 drops below approximately 25% of its rated normal value, and permits a closing operation of the circui breaker only if this voltage rises above approximately 80% of its normal rated value. The fingers 83 and 50 may have cam surfaces 89 and 9| respectively which facilitate passage of the pin 92 to locking position with respect to each of the fingers.

For operating the sectionalizing circuit breaker 4b, a bell crank I is pivoted for movement about a fixed support I02. At one end, the bell crank I00 carries a fork I34 which embraces the pin I0 for moving the arm 50' between its open and closed positions. The other end of the bell crank I00 is connected to an armature I08, the weight of which normally biases the operating arm 50 towards its closed position. The armature I05 is associated with a magnetic structure I08 having an energizing winding I I0. This energizing winding may be connected through a suitable relay for energization in accordance with any desired variable quantity, such as current, voltage, or direction of power flow. For the purpose of this discussion, it is assumed that the energizing winding H0 is connected for energization in accordance with current flowing through the contacts 20 and 22' of the sectionalizing circuit breaker 4?).

For controlling the energization of the winding I I0 a relay which may take the form of a bimetallic spring element I I2, is provided. This bimetallic spring element has one end attached to a fixed support H4 and carries a movable contact H6 at its free end. Under normal conditions, the movable contact II6 is biased in engagement with a fixed contact H8. The bimetallic spring element H2 and the bimetallic spring 64 are connected in series with one of the pairs of contacts 20' and 22 for energization in accordance with the current flowing therethrough.

Current flowing through the bimetallic spring element H2 heats the element and actuates the free end of the element in the direction of the arrow I20. This direction is such that an excessive current flowing through the spring element separates the movable contact IIB from the fixed contact I I8.

It will be observed that the energizing Winding H0 is connected across the contacts H6 and H8. Consequently, separation of these contacts places the energizing winding in series with the bimetallic spring element H2, and the bimetallic spring 64 for energization in accordance with current flowing through the contacts 20 and 22. Energization of the winding H0, in turn, operates to attract the armature I06 and move the operating arm 50' towards its open position. Such movement of the operating arm 50' separates the contacts 20 and 22' of the sectionalizing circuit breaker 41).

It is desirable that the relay or bimetallic spring element I I2 have a time delay and preferably an inverse time delay in its operation. Since bimetallic spring elements inherently have a time delay which varies inversely with the current passing therethrough, it follows that the bimetallic spring element H2 provides the desired characteristics.

Some faults resulting in an opening operation of a circuit breaker are self -clearing. For this and other reasons, it is desirable that the sectionalizing circuit breaker 4b be permitted to reclose after a brief delay. Such operation may be obtained by positioning a lug I22 on the bimetallic Spring element I I2. A link 98 having one end supported on a fixed pivot is pivotally connected to one end of a second link 99, of which the other end is held by pin III on arm 50'. The end of link 98 is engaged and locked by lug I22 when the bimetal H2 is deflected by heat, thereby locking breaker 4b in the open position until bimetal I I2 cools after once energizing winding H0 to open the breaker. By inspection of Fig. 2, it will be observed that when current flow through the bi metallic spring element II2 exceeds a predetermined excessive value, the contacts H6 and H8 separate to energize the winding I ID. This energization of the winding III), in turn, operates to attract the armature I05 and to move the operating arm 50 to its open position. The movement of the operating arm 50 to it open position carries the levers 98 and 99 into the positions indicated by dotted lines. In this position, the lever 98 is held against a return movement by means of the lug I22. A cam surface I03 on the lever 98 facilitates movement of the lever into locking position.

Since the circuit breaker 4b has opened, the flow of current through the bimetallic spring element H2 ceases. As the spring element cools, it moves in a direction opposite to that indicated by the arrow I20 to carry the lug I22 away from the path of movement of the lever 98. Consequently, the lug I22 prevents a reclosure of the sectionalizing circuit breaker M) for a time sufficient to permit withdrawal of the lug I22 from the path of movement of the lever 98. After such withdrawal, the bias of the armature I06 operating through the bell crank I00 and the bias of the spring 45 return the operating arm 50 to its open position.

To increase the time delay required to reclose the circuit breaker 4b, the contact II 8 may be spring mounted to follow the movable contact H6 for a short distance. For example, the contact H8 may be mounted on one end of a cantilever spring II9 which is biased towards a stop I2I. This construction permits the lug I22 to advance for a slightly greater distance into the path of movement of the lever 98.

As previously pointed out, operation of the transformer circuit breaker 4a is determined in part by the force applied to the link 68. This link extends between the pins III and I0. The force applied to the transformer circuit breaker 4a through the link 68 is determined by the movement of the operating arm 50 of the sectionalizing circuit breaker 4?). For this reason, an operation of the transformer circuit breaker 4a through the link 68 takes place only in response to an operation of the sectionalizing circuit breaker 4b.

It will be recalled that operation of the lock I6 prevents an actuation of the operating arm 50 of the transformer circuit breaker la under certain conditions.

The operation of the link I58 may be reviewed briefly. Assuming that the circuit breakers la and 4b are in the positions illustrated in Fig. 2 in full lines, a movement of the operating arm 50' to its dotted position opens the sectionalizing circuit breaker 4b. If the lock I6 happens to be in its dotted-line position, which corresponds to a loss of voltage across the secondary winding of the transformer 4, the movement of the arm 50' operates through the link 68 to pull the arm 50 of the transformer circuit breaker to to its dotted-line position. Consequently, the

opening operation of the sectionalizing circuit.

breaker tbresults. in an opening operation: of; the transformer: circuit breaker to.

However, if. the lock It: happens to be in its fullline positi'on,.the locking. finger 88 prevents movement of linkage. 94, 9.5, 911 and of. theoperat'- ing arms 30,. 32- and the movement of. the operatin; arm; 50" to its open position results in a lengthening. and tensioning of the spring "8;. It will, be understood. that the spring 46 biases: the operating. arms 32 of the transformer circuit hreainar towards: its open position. Should the: lock 16 subsequently move to its dottedkline position, which indicates a loss of voltage across the: secondary of the transformer 4 the bias exerted by the: spring 4E operatesto puil the operating arms: 30, 32 of the transformer circuit breaker 4a. to its open-circuit position, thereby opening the transformer circuit breaker;

Letit be assumed. next that the sectionalizing circuit breaker 4b is in an open condition and that the lever 98- is locked by means of the lug I22. the bimetallic spring element H2 cools, the lug I22 moves from the path of the lever 98 and permits areclosure oi" the secti'onalizing circuit breaker 4b. It. the transformer circuit breaker do is m the position shown in full lines imFig. 2 at the time the lug I22 moves from the path of the lever 98; reclosure of the sectionalizmg circuit breakerilb merely relievesthe tensionof'the spring 46. v

should the transformer circuit breaker to be locked open by means of the locking finger 90 at the time the lug I22 is withdrawn from the path of movement of the lever 96} the reclosing operation of the sectionalizing circuit breaker 4b moves the operating arm of the transformer circuit breaker 422- towards its closed position but linkage. 94, 91 holds the contact 22 open. Subsequent'operationof the-locking finger 90-to clear the lever 98 permits a reclosure of the transformer circuit breaker 4a under the bias of the spring 46;

From the brief analysis; it will be appreciated that the aforesaid operation or the trans-former circuit breaker to occurs only in response toan operation of the sectionalizing circuit breaker 41);, Furthermore, theoperation 01' the transformer-circuit breaker to may be delayed or prevented by operationof the-lock 16.

If the lug or 60- is" permanently positioned in the path of the tongue 62 or 62', as shown in Fig. 2, the foregoinganalysis covers thecomplete operation of the circuit breakers illustrated in Fig. 2'. However, in many systems it is'desirable that a further control of the operations of the circuit breakers be effected by a suitable movement of the lug 60- or 60'. To this end the bimetallic springs 64 and 64 are connected respectively in series with the contacts of the associated circuit breakers 4a or 4b; For this reason; each of the'bimetallic springs is heated in accordance with current flowing through the associated circuit breaker contacts. If the current flowing through the contacts of one of the circuit breakers exceeds a predetermined excessive value; the heating of the associated bimetallic spring moves the associated lug BO-or' 60" from the path of movement of the tongue 82 or 62', thereby resulting in opening of the associated circuit breaker. I

Inthe specific system herein discussed, the time delay of the bimetallic spring 84 or 64' is substantially'greater than that oi'th'e bimetallic springelement H2; For this reason, the bimetallicspring element ll2 operates first to open the associated circuit breaker or circuit breakers in an eitort to clear the faulty portion: at thesystem. Should the fault persist, the bimetallic spring 64 01 M operates to open the associated circuit breaker and prevent further recl'osure thereof; As a specific example, the: bimetallic springs 64 and M may be proportioned tapermit three or fouropening and closing operations under the. control of the bimetallic spring element H 2 prior to opening otthe bimetallicspring Merit;

From: the foregoing description; it is believed ti iat the complete operation of thesystem illustrated in Fig. I may: beset forth. Let it be assumed first that a. fault F'occurs between the transformers 4 and 5 as shown in Fig. I. The resulting excessive flow of current tends to dei'icct the bimetallic springs G t, 6'4 and- 21 Since the bimetallic spring H2 has a shorter time delay than that" of the bimetallic spring 64 or 94 it separatesits contacts I'l=6 and l l8- to energize the winding H02 Energization of the winding Hl't operates through the bell crank" III'II toopen the sectiohaiizing circuit breaker ii In addition, the lug; I422 moves intop'osit'i'orr for locking thesectionali zing circuit breaker lb-open for a time sufficient to permit cooling of the bimetallic spring H 2. At theend of this interval, the sectionalizingcircuit breaker 4brecl'cses. Since voltage is present at thetransformer 4*, the locking finger ill! prevents opening of the transformer circuit breaker to. 7

I 1 the-fault or overload persists, the bimetallic spring- H 2 again is heated to produce a second opening and reclosureoperation of the section alizing circuit breaker 4b. This condition continues until the bimetallic spring 84 heatssuflicientl'y to tripthesectionalizing circuit breaker 4b and prevent further operation thereof; As previously pointed out, the thermal characterist'icsof the bimetallicsp'ring 64 may be=selected to permit approximately three or four opening and closing operations of the bimetallic spring H2 prior to anopening operation of the spring G t". Ii the bimetallic spring 64" carries more current under these conditions than the bimetallic spring 6 1, or if" the former has a; slightly shorter time delay; the sectionalizing' circuit breaker 412* trips before the bimetallic spring 64 can open the transformer circuit breaker; Consequently; the transformer circuit breaker la remains closed and continues to supply electrical energy to the load circuit. 2

Assume next that the fault F is accompanied by a loss of voltage at the transformer 4". The sectionalizing circuit breaker 4b again opens as above set forth. However, since a loss of voltage results in a movement of' the lock. 16 to the positionin'dicated in dotted lines in Fig; 2, the opening operation of the. sectionaliz ing circuit: breaker 4b results in anopening operation oil the transformer circuit breaker 4a; The sectionalizing circuit breaker l'b' again goes through its'reclosing cycle andfinally remains closed or'trlps out as previously setforth". However; the transformer. circuit breaker'ta remains open for'the reason that the locking. finger remains in the path of movement ofthe pin 92 (see Fig. 2). Should full voltage appear across the secondary winding: of the transformer 4 after the sectiona'lizing breaker 4!; has reclosed,the lock 'Hilis picked up to permit' reclosure of the transformer circuit breaker ta. 7 It; will be observed that" the fault F'is directly connected to the circuit breakers 5a and 5b.

Since operation of the sectionalizing circuit breaker b does not affect the connection of the fault to the transformer circuit breaker 5a, the bimetallic spring 64 of the transformer circuit breaker 5a finally trips to disconnect the transformer 5 from the fault regardless of th operation of the sectionalizing circuit breaker 52).

Since the sectionalizing circuit breaker 5b carries fault current, it does through an opening and reclosing cycle similar to that of the sectionalizing circuit breaker 4b and either recloses permanently in the event that the fault is self-clearing or is permanently opened by its bimetallic spring 64'. In this manner, the adjacent breakers operate to clear a faulty portion of the distribution system.

It should be observed further that after an opening operation of the sectionalizing circuit breaker under the influence of the bimetallic spring 64, the transformer circuit breaker 4a may be either locked open by operation of the locking finger 90, or it may reclose if voltage is present across the secondary winding of the associated transformer. In the latter case, the associated transformer is fully protected by operation of the bimetallic spring 64 associated with the transformer circuit breaker 4a.

After an opening operation initiated by the bimetallic springs 64 and 64, the circuit breakers may be reset manually to permit a subsequent reclosure thereof. Such resetting may be effected by moving the operating arms 50 and 50 of the circuit breakers to their open positions and then releasing the arms. Such operation relocks the tongues 62 and 62 beneath the associated lugs 60 and 60.

Although the ends of the load circuit are illustrated in Fig. 1 as unconnected, these ends may be connected to form a loop as hereinafter pointed out.

In the modification shown in Fig. 4, the transformers are associated with a plurality of sources of electrical energy I26 and I28 through feeder circuits I30 and I32. Feeder circuit breakers I34 and I36 are positioned in the feeder circuits adjacent the sources to control the connection of the feeder circuits to the sources. Although the feeder circuits may be connected to a common source of energy through different routes, for the purpose of illustration the feeder circuits are shown connected to separate sources of energy. In the specific example illustrated in Fig. 4, the transformers 4, 6 and 8 are energized through the feeder circuit I30 from the source of energy I26. The remaining transformers are energized through the feeder circuit I32 from the source of energy I23.

Since the load circuits of Fig. 4 may be energized from either of the feeder circuits, upon the occurrence of a fault on one of the feeder circuits it is desirable that only the faulty feeder circuit be removed from service and that the remaining feeder circuit together with the associated transformers, remain in service.

This desirable operation is provided by the apparatus illustrated in Fig. 2. Furthermore, the lock I6 is of particular value when employed in a system similar to that of Fig. 4, as will be apparent from a brief discussion of the operation of the system shown in Fig. 4.

I Let it be assumed that the system of Fig. 4 is operating normally and receiving energy from both feeders of the circuits I30 and I32. If a fault occurs on one of the feeder circuits, such as the feeder circuit I30, electrical energy flows directly from the source I26 to the fault. Furthermore, electrical energy flows from the source I28 through the feeder circuit I32, the transformers 5, I and 9, the tie circuit I1 and the transformers 4, 6 and B to the same fault.

The feeder circuit breaker I34 opens in response to the fault current flowing from the source I26 to the fault on the associated feeder circuit I30. This feeder circuit breaker may be of a conventional reclosing type which recloses and opens a predetermined number of times and finally locks open if the fault fails to clear within the reclosing cycle thereof.

Fault currents flowing through the sectionalizing circuit breakers 4b and 9b heat the associated bimetallic spring elements H2 and open these circuit breakers. Since the transformer circuit breaker 9a is connected to the sound feeder circuit I32, voltage is present at the circuit breaker and its lock I6 retains the circuit breakerin closed condition. Consequently, the transformer 9 continues to supply electrical energy to the various loads.

However, the transformer circuit breaker 4a is connected to the faulty feeder circuit I30 and the magnetic structure 82 associated therewith is deenergized. For this reason, the lock I6 associated with the transformer circuit breaker 4a is actuated by its spring 85 to the position illustrated in dotted lines in Fig. 2. With the lock in this position, the opening operation of the associated sectionalizing circuit breaker 4b operates through the link 68 to open the transformer circuit breaker 4a.

At the end of the time delays determined by the cooling of the bimetallic spring elements II2, the sectionalizing circuit breakers 4b and 9b reclose to restore the loop circuit for energization from the transformers 5, I and 9 associated with the sound feeder circuit I32. Since no voltage is present across the secondary winding of the transformer 4, the lock I6 prevents reclosure of the transformer circuit breaker 40.

If the fault on the feeder circuit I30 clears within the reclosing cycle of the feeder circuit breaker I34, the feeder circuit breaker recloses and remain closed to energize the transformer 4. Such energization operates to pick .up the lock I6 associated with the transformer circuit breaker 4a and results in reclosure of this transformer circuit breaker. The system consequently is restored for full normal operation.

In the event that the fault on the feeder circuit I30 is permanent the feeder circuit breaker I34 goes through its reclosing cycle and finally locks open. This means that the transformer circuit breaker 4a remains open until the faulty feeder circuit I30 is repaired and the feeder circuit breaker I34 is manually reclosed. Manual reclosure of the feeder circuit breaker I34 restores voltage to the transformer 4 and permits reclosure of the transformer circuit breaker 4a. Since the transformer circuit breakers 6a and 8a also are connected to the faulty feeder circuit, the operation of these transformer circuit breakers and their associated sectionalizing circuit breakers are similar to that discussed for the transformer circuit breaker 4a and its sectionalizing circuit breaker 4b.

Let it be assumed next that thefault F occurs on the tie circuit II between the sectionalizing circuit breakers 4b and 5b. Since the sectionalizing circuit breakers 4b and 5b are closest to the fault, they will be the first circuit breakers to open. It will be noted that under these condi tions voltage is resent at bothof. the transformer ircuit, bre ke a, and- 1- q nsequ n l t e associated; locks 16' of these transformer circuit breakersfretain the circuit breakers in closed condition despite the opening of the sectionalizing circuit breakers lb and 5b.

After opening, the sectionalizing circuit breaker 4b and 5b gothrough their reclosing cycles. If the fault E clears prior to; completion of these reclosing cycles, the sectionalizing circuit breakers close and remain closed to restore the complete system for normal operation. Should the faultFbe permanent, the bimetallic elements 64 associatedwith' the sectionalizing circuit breakers 4b and Sb finally open these circuit breakers and prevent further reclosure thereof,

Theopening of the sectionalizing circuit breakers 4b and 5b isolates the fault F from the transformer circuit breaker 4a. Consequently, the fault F has no further eifect on this circuit breaker.

It should be observed, however, that the fault F still is connected directly to the transformer circuit breaker 5a. As previously pointed out, if no bimetallic elements 64 are provided for the transformer circuit breakers and if the levers 40 are maintained permanently in the positions illustrated in full lines in Fig. 2, the transformer circuit breakers remain closed as long as voltage is present to energize their respective magnetic structures 82. In such a case the transformer circuit breaker So would remain closed for the fault F, and the fuses l associated with the transformer would blow to deenergize the transformer. Deenergization of the transformer results in release of the lock 16 associated with the transformer circuit breaker 5a and permits opening of this circuit breaker under the influence of the tension stored in the spring 46 when the sectionalizing circuit breaker 5b opened.

Under these circumstances, the transformer circuit breaker 5a is never called upon to open load current. For this reason the transformer circuit breaker 4a need not be designed to interrupt heavy currents and may be of simplified construction. In other words, the transformer circuit breaker would open only in response to absence of voltage at the associated transformer. Since this generally indicates that no current flows through the contacts of the associated transformer breaker, the control afforded by the lock 16 may be employed to reduce substantially the current interrupting capacity requirements of the associated transformer circuit breaker. A previously pointed out, the magnetic structure 82 may be energized in accordance with both voltage and current present at the associated transformer to prevent release of the lock 16 for an opening operation of the associated transformer circuit breaker unless both the voltage present at the transformer and the current flowing therethrough are below predetermined values. Utilization of both current and voltage for controlling the opening of a transformer circuit breaker in this manner is discussed in greater detail in the aforesaid Parsons application.

In the specific embodiment herein illustrated, each of the transformer circuit breakers is provided with one of the bimetallic elements 64' for opening the associated circuit breaker. With such a construction current flowing through the transformer circuit breaker 5a to the fault F heats the associated bimetallic spring 64. at the end of the time delay for which the bimetallic element, 64. is designed, the transformer circuit breaker 5a opens to, disconnect. the, transformer 5 from the fault. Therefore, the system illustrated in F g, 4 continues-in operation except for the transformer, 5-and t e small. portion ofthe system associated with the load circuit l2;

Although, the application has been, discussed with reference to certain specific, embodiments thereof; numerous modifications are possible. 'Ifherefore, th e invention is to. be restricted only y. the. pp nded claims.when.interpretedinview of 'theprior art.

I laimas myinventio 1 In combination, afirst, circuit breaker provided with. a, mechanism to open and. close, itsv separable contacts, asecond, circuit breaker, having a moving. separable. contact and an. actuating mechanism andresilient means linking it to said moving separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means for controlling said lock.

2. In combination, a first circuit breaker provided with a mechanism .to open and close its separable contacts, a second circuit breaker having a moving separable contact and an actuating mechanism and resilient means linking it to said moving separable contact, a non-resilient link interconnecting the mechanism of the first. said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means governed by the electrical circuit containing said second circuit breaker for controlling said lock.

3. In combination, a first circuit breaker provided with a mechanism to open and close its separable contacts, a second circuit having a moving separable contact and an opening and closing lever and resilient means linking it to said movable separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means for controlling said lock.

4. In combination, a first circuit breaker provided with a mechanism to open and close its separable contacts, a second circuit breaker having a moving separable contact and an opening and closing lever and resilient means linking it to said movable separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means governed by the electrical circuit containing said second circuit breaker for controlling said lock.

5. In combination, a first circuit breaker provided with a mechanism to open and close its separable contacts and having a load-responsive element adapted to open it, a second circuit breaker having a moving separable contact and an actuating mechanism and resilient means linking it to said moving separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means governed by the electrical circuit containing said second circuit breaker for controlling said lock.

6. In combination, a first circuit breaker provided with a mechanism to open and close its separable contacts and having a load-responsive device adapted to open it, a second circuit breaker having a movin separable contact and an opening and closing lever and resilient means linking it to said movable separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and

electroresponsive means for controlling said lock.

7. In combination, a first circuit breaker provided with a mechanism to open and close its separable contacts and having a load-responsive device adapted to open it, a second circuit breaker having a moving separable contact and an opening and closing lever and resilient means linking it linked to said movable separable contact, a non-resilient link interconnecting the mechanism of the first said circuit breaker to said mechanism of said second circuit breaker, a lock for holding said moving contact unmoved notwithstanding the movement of said link, and electroresponsive means governed by the circuit connected to the first said circuit breaker.

JOHN W. MAY. 

